dual monitor problem

[wmeyer48]

I am running LinuxMint and just updated, then upgraded the kernel. With kernel 5.4, both monitors worked fine. With kernel 5.11.16, both are recognized, but only one shows any video. I am very new to Linux, but did collect this info....

System: Kernel: 5.11.16-051116-generic x86_64 bits: 64 compiler: N/A Desktop: Cinnamon 4.8.6
wm: muffin dm: LightDM Distro: Linux Mint 20.1 Ulyssa base: Ubuntu 20.04 focal
Machine: Type: Desktop Mobo: ASRock model: X570 Steel Legend WiFi ax serial: <filter>
UEFI: American Megatrends v: P3.31 date: 11/06/2020
Battery: Device-1: hidpp_battery_0 model: Logitech Wireless Mouse M325 serial: <filter>
charge: 55% (should be ignored) status: Discharging
CPU: Topology: 8-Core model: AMD Ryzen 7 3800X bits: 64 type: MT MCP arch: Zen
L2 cache: 4096 KiB
flags: avx avx2 lm nx pae sse sse2 sse3 sse4_1 sse4_2 sse4a ssse3 svm bogomips: 124566
Speed: 2536 MHz min/max: 2200/3900 MHz Core speeds (MHz): 1: 2536 2: 1864 3: 2052
4: 1879 5: 2196 6: 2196 7: 2196 8: 2195 9: 1902 10: 2013 11: 2191 12: 2192 13: 2196
14: 2191 15: 2196 16: 2780
Graphics: Device-1: AMD Baffin [Radeon RX 550 640SP / RX 560/560X] vendor: XFX Pine
driver: amdgpu v: kernel bus ID: 0e:00.0 chip ID: 1002:67ff
Display: x11 server: X.Org 1.20.9 driver: amdgpu,ati unloaded: fbdev,modesetting,vesa
resolution: 2560x1440~60Hz, 1920x1080~60Hz
OpenGL:
renderer: Radeon RX 550 Series (POLARIS11 DRM 3.40.0 5.11.16-051116-generic LLVM 11.0.0)
v: 4.6 Mesa 20.2.6 direct render: Yes

[SMG]

I am running LinuxMint and just updated, then upgraded the kernel.

For what reason did you change to an unsupported kernel? You ignored the advice in the other thread to try the supported 5.8 kernel. The 5.4 kernel is also supported. The 5.11.16 (this thread) and the 5.10.17 (which you mentioned in the other thread) are not supported kernels.